Native full encryption through zfs. That was my main reason. Zfs is well integrated in BSD. Something that will not happen soon in linux based on Linus latest comments that zfs has legal issue with linux
It is there on Linux, and it has the encryption patches.
Basically the same reasons i had 20 years ago when I switched from Microsoft Windows to Linux. Except for the money reason, which in the era of Win98, Win2k wasn't that big of a problem.